1. Field of the Invention
The present invention concerns compositions and methods for plant growth promotion. More particularly the invention concerns microbial plant growth promoting compositions and methods for ther use.
2. Description of the Background Art
Since man first began cultivating plant life, there has been an interest in promoting plant growth and increasing yields. This is particularly important in northern climates having limited growing seasons.
Various avenues have been pursued in attempts to promote plant growth. The use of microbes to achieve this result has been of great interest, particularly the use of nitrogen-fixing bacteria. Various means have been devised for contacting the roots of plants with nitrogen-fixing bacteria including inoculation of soil with such bacteria and treating seeds with bacteria-containing compositions.
In addition to nitrogen-fixing bacteria, it is believed that other microorganisms found in the soil benefit plant growth. Although the exact mechanism of this beneficial action is not known, it has been proposed that such microorganisms break down complex soil components to nutrients that are assimilable by the plants. The conditions favoring microbial growth in tropical jungle soils are thought to partially account for the lush plant growth in those regions.
Algae have also been employed for improving soil conditions and hence plant growth. For example, U.S. Pat. 4,336,051 to Marguez describes soil-improving compositions containing gelidum type marine algae. Among the stated purposes of these compositions are to produce beneficial enzymes and to competitively inhibit the growth of pathogenic bacteria.
In light of current and foreseeable demands on the world food supply, there is a continuing interest in developing methods and means of improving plant productivity.